Adding a wrapper for kseg, which enables automatic language settings

I wrote a small wrapper script for kseg to enable automatic language settings.
This script overwrites the "Language" entry in ~/.kseg, which is determined automatically
from the LANG environment variable. The default LANG is set at boot time, but we can
switch to another language at any time by changing it, e.g,

    $ LANG=ja_JP.UTF-8 kseg

The wrapper is included in the live image as "/usr/local/bin/kseg". I'm not sure we should
choose another name, but then, we will have to edit the "kseg.desktop", too.

You can try the script easily by copying it as /usr/loca/bin/kseg on your live system,
before re-building the image (without modifying any other files).